Facemask and Respirator in Reducing the Spread of Respiratory Viruses; a Systematic Review

Introduction: Respiratory viruses spread fast, and some manners have been recommended for reducing the spread of these viruses, including the use of a facemask or respirator, maintaining hand hygiene, and perfoming social distancing. This systematic review aimed to assess the impact of facemasks and respirators on reducing the spread of respiratory viruses. Methods: We conducted a systematic review using MeSH terms, and reported findings according to PRISMA. PubMed, Embase, Cochrane Library, Scopus, ProQuest, Web of Science(WoS), and Google Scholar were searched for articles published between 2009 and 2020. Two independent reviewers determined whether the studies met inclusion criteria. The risk of bias of studies was assessed using Newcastle-Ottawa (NOS) and Consolidated Standards of Reporting Trials (CONSORT). Results: A total of 1505 articles were initially retrieved and 10 were finally included in our analysis (sample size: 3065). 96.8% of non-infected participants used facemask or respirator in contact with people infected with a respiratory virus, facemask and respirator have a significant effect on reducing the spread of respiratory viruses. Conclusion: Evidence support that using a facemask or respirator can reduce the spread of all types of respiratory viruses; therefore, this result can be generalized to the present pandemic of a respiratory virus (SARS-COV-2) and it is recommended to use a facemask or respirator for reducing the spread of this respiratory virus.


Introduction
In recent decades, humans have been threatened by a variety of viruses that lead to acute respiratory infections affecting human life and human societies, sometimes leading to death. There are several routes of respiratory virus transmission: contact, droplet, and aerosol. Respiratory viral infections cause a wide range of overlapping symptoms, known as acute respiratory illness (ARI) or, usually (more commonly) "the common cold" as a whole, which is chiefly mild but may cause severe illness and death (1). To protect themselves against such viruses, humans have offered a variety of strategies, from wearing facemasks and home quarantine to producing drugs and making the body resistant to such particles using appropriate vaccines. When specific vaccines or disinfection treatments are not available, the use of non-drug interventions, such as wearing respiratory personal protective equipment (RPPE), is important for protecting and reducing the occupational risk of health care workers (HCWs) against respiratory infections (2). Common types of PPE include surgical masks and respirators. It should be noted that surgical masks are loose and disposable and create a physical barrier between the wear-ers' mouth and nose and environmental contaminants (large respiratory droplets or sprays of blood and body fluids). They are not designed to filter out small airborne particles and have very different level of protection (3,4). In this regard, the results of some studies have shown that daily use of surgical masks in all areas of the hospital is important in reducing swine flu infection, such measures at least prevent touching the mucous membranes of the nose and mouth with the fingers and such unconscious behaviors are less common (5,6). These masks should be replaced as soon as they get wet or at least every four hours (3). In contrast, n95 respirators or their European equivalent, FFP2-3 prevent the penetration of at least 95% of aerosols less than 5 mm. But due to resistance to respiration and heat their long-term use is intolerable for HCWs (4). They should be worn for less than 8 hours during the day and should not be reused if they get wet (3). Besides, the equipment needs to fit completely on the face. It is very difficult to use this equipment in people with facial hair or beard and children, and is not recommended for the elderly, claustrophobic, and people with lung disease. Powered air-purifying respirators (PAPRs) have blowers that provide positive pressure airflow through the filter. They do not need to fully fit, and they protect the head and neck contiguously. One of its disadvantages is being the most expensive PPE. The world is currently suffering from a pandemic (7), caused by a virus now known as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) (named by the International Committee on Taxonomy of Viruses (ICTV)), Which has a phylogenetic similarity to SARS-CoV and its resulting disease is called COVID-19 (8,9). Recommendations for the use of surgical masks during the present coronavirus disease pandemic include: people with suspected or confirmed respiratory infection COVID-19 symptoms; people in contact with HCWs or first-aid workers, and HCWs in contact with people with symptoms of respiratory infection (3). The present study aims to assess the effect of wearing a facemask on the reduction of incidence and prevention of infection with respiratory viruses such as SARS-CoV-2.

Methods
This systematic review is reported based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (10).

Search strategy
In this systematic review, Google Scholar, PubMed, Embase, Cochrane Library, Scopus, ProQuest, and Web of Science (WoS) were searched for articles published between 2009 and 2020. Boolean operators such as "AND" and "OR" were used to make different combinations for search (11). In addition, we searched using the following terms:

Type of studies
All studies published between 2009 and 2020, which were conducted to assess the effect of facemask on preventing the of spread respiratory viruses and reported the number or percentage of participants using a facemask and getting or not getting infected with a respiratory virus, were included in the study. Publications such as reviews, letters, comments, and case reports and studies that were conducted just for comparing different types of facemasks, or evaluated people with a tissue graft, or their sample size was not clear were excluded from the study. There were no language restrictions for using and entering articles in this study. If the language used in an article was not Persian or English, we asked a translator to translate the article.

Types of participants
The studies were selected if their participants were: -people in contact with those infected with respiratory virusespeople who were members of specific groups such as healthcare personnel, emergency department and general ward staff, public health workers, Hajj pilgrims

Types of interventions
The studies were reviewed if: -participants used PPE -measured the effect of facemask or PPE on preventing transmission of respiratory viruses

Type of outcome measure
All studies measured the number and percentage of participants who used facemask, PPE, vaccine, and distance or did not use them and were infected after being in contact with a person infected with respiratory viruses.

Study selection
The title and abstract of all studies retrieved during the electronic and manual follow-up search process were assessed based on the inclusion criteria. The full texts of relevant papers were examined based on the mentioned criteria.

Quality assessment
In this study, the quality of Cohort and Cross-Sectional studies was assessed according to the Newcastle-Ottawa scale (NOS) (12); and the quality of Controlled-Trial studies was assessed based on CONSORT. A maximum of ten stars was given to each study based on the NOS. A maximum of five stars was given to selection (including sample size, nonrespondents, and ascertainment of the exposure). A maximum of two stars was given to comparability (including the study control for the most important factor). A maximum of three stars was given to outcome (including assessment of the outcome and statistical test). Studies of high-quality score nine or ten stars, studies with a score of seven or eight stars were considered to be of medium quality, and studies scoring less than six stars were considered to be of low quality (13). The CONSORT checklist was also used to report the standard clinical trial studies. This checklist contains 24 questions and a score of 0 or 1 is given to every question. If a study scored above 15, it was included in the study and thoe scoring 15 and below were excluded (14). The quality score for each article is shown in Table 1.

Data extraction
Two investigators independently searched for relevant scientific publications, carried out validity assessments, and resolved any disagreements by consulting a third investigator (15). Data were collected as follows: 1. Research information (reference, type of study, location, and sample size (Male, Female)) 2. Characteristics of the participants (population, and age) 3. Intervention and comparison of the details (type of viruses, type of contact with an infected person, PPE type, facemask type) 4. Outcome measures (number of PPE types, number of facemask types, infected participants using facemask, distance, time of contact with person, time of using facemask, and vaccinated people)

Statistical analysis
We calculated the number and percentage of infected and non-infected people in all included studies and reported them in tables.

Results
The systematic search in the databases identified 1505 articles. After reviewing their titles and abstracts, 753 duplicate articles, 654 records with undesirable study types, and 88 irrelevant articles were removed. Finally, 10 articles (Sample Size=3065) were included in the systematic review. The flowchart of studies included in this review is shown in Figure 1. The characteristics of included studies are presented in Table 1

Factors examined in the studies
The factors presented in table one include the author's name, study design, type of population, sample size, age, result, and quality score. Table two includes type of virus, type of contact with an infected person, PPE type, facemask type, and infected participants who used masks after contact with the patient.

Type of Contact
The type of contact with an infected person was assessed in nine articles and varied in different studies. Generally, the contact was between health care workers and infected persons (16, 17, 20, 22, 24), emergency department and general ward (18), public health workers (19), Hajj pilgrims (21), and household contact (23, 25), contact with aerosol, and skinto-skin contact.

PPE Type
The PPE type was mentioned in all assessed studies.

The number of infected people who used a facemask or N95 respirator
Generally, 3.2% of participants who wore a facemask became infected with the respiratory virus through contact with an infected person. In studies that all participants wore surgical masks (18, 19, 21, 23, 25), 0.3% of them became infected. In studies that all participants wore N95 respirators (17-20, 22, 24), 1.4% became infected. 0.2% of participants who wore N95 respirators and surgical masks became infected (18, 19). 1.7% of participants who wore N95 respirators and medical masks became infected (20). 0.3% of participants who wore N95 respirators and other facemasks became infected (17) and 0.5% of participants who wore P2 masks and surgical masks became infected (25). Also, some studies did not mention the effect of each facemask on preventing virus spread and the percentage of using each type of facemask so it was not possible to draw a precise conclusion about the quality and effectiveness of each type of facemask based on the mentioned statistics.

Distance and time of contact
Distance between people and the duration of contact with an infected person was mentioned in five studies (16, 19-22). We could not assess the effect of distance and duration of contact on preventing the spread of virus because these studies did not mention the count of the infected participants based on distance and duration of contact.

Duration of using a facemask and vaccinated
The duration of facemask use and the number of vaccinated people were evaluated in five studies (17, 20, 23-25). However, these studies did not mention the effect of vaccination and duration of facemask use on prevention of virus infection.

Discussion
The results of the present study showed that using facemask or respirators has a preventive effect on the spread of respiratory viruses including SARS-CoV-2, MERS-CoV, Rhinovirus, Influenza A virus (H1N1), Influenza B viruses, Parainfluenza 1,2 and 3 viruses, Enteroviruses, Adenoviruses, Human metapneumoviruses, Respiratory syncytial viruses A/B, Coronaviruses, Picornaviruses, and Enteroviruses. Moreover, the percentage of transmission of respiratory viruses in people who wore any type of facemask or N95, respectively, was 0.3% in the surgical mask group, 1.4% in the N95 respirators group, 0.2% in N95 respirators and surgical mask group, 1.7% in N95 respirators and medical mask group, 0.3% in N95 respirators and another facemask group, and 0.5% in P2 masks and surgical mask group. In COVID-19 disease pandemic, due to the lack of access to appropriate antiviral medications and the lack of a suitable vaccine, infection control was the most important way to control it (26). Therefore, many countries performed non-drug interventions and early control strategies that included the use of facemasks and double key actions such as hand hygiene and temporary closure of schools and offices as recommended by the international scientific communities (25). SARS-CoV-2 transfer is mainly through direct transfer of droplets by sneezing and coughing and contact; also, airborne transfer is possible via aerosol-generating procedures (AGPs) (24, 27, 28). Moreover, it has been shown that large droplets could accelerate the transfer of fomite and suspended in the air (28). Besides, these large droplets can move up to two meters or eight meters (28). In this regard, Liu et al. showed that a high concentration of virus is in the air sample of the patient's toilet and in the environment in which HCWs their PPE (29). Hence, virus-infected particles are more likely to be suspended in the air in places where the airflow is turbulent and patients with or without symptoms or in the pre-symptom phase of COVID-19 have many referrals (30). And health care workers are more likely to become infected (46). In this regard, the rate of Influenza virus transmission between HCWs in the H1N1 pandemic were 14%, yet 67% of them did not have any signs (31). Besides, most positive cases were between outpatient and Ancillary HCWs and HCWs who used surgical masks or N95 respirators were seronegative (31). This indicates that they'd not use PPE such as facemasks (31). Moreover, Ki et al. showed that emergency department staff had more exposure to respiratory infections MERS disease compared to the internal department staff (In terms of time, the medical staff of the emergency department spent more time with the index patient than those working in the internal department, eight hours versus one hour). However, the rate of being stricken with disease was 3% vs 16.7%, respectively, because 93% of emergency department staff used surgical masks and 95% of them used hand wash but only 8% of the general department staff used surgical masks (32). It should be noted that in studies, the proportion of infected HCWs among the confirmed cases of Coronavirus disease-2019 is 10% in Italy, 20% in Spain, and 40% in the United States (33). Infected HCWs can be a source of infection for other HCWs and patients (4). Therefore, the protection of HCWs and the provision of PPE are of particular importance to maintaining ongoing care and the function of the health care system. On another hand, Liu et al. showed that the rate of RNA virus was reduced by performing a disinfection procedure in the PPE room (29). This emphasizes the effect of environmental disinfection in reduction of virus transmission (29). Therefore, in addition to providing PPE for HCWs, health organizations should emphasize continuous training on donning and doffing for effective protection (34,35). Study results showed that the infection control team of the hospital can significantly reduce the transmission of the disease between HCWs through early diagnosis and identifying index cases among patients and explaining preventive actions to them, giving early leave to sick staff, or at least giving them some recommendations such as maintaining social distance with other staff, hand hygiene observation, and wearing facemask during a disease outbreak, and monitoring the adherence to infection control methods (26). In addition to HCWs' awareness, climate condition is another factor that obstructs the correct use of respiratory protection equipment between HCWs (36). Studies state that in a household setting, due to the increased cumulative exposure time of index patients with family members, the possibility of transmitting viral respiratory infections is higher (37,38). In this regard, results of studies showed that if family members perform non-drug interventions (such as wearing facemask and maintaining hand hygiene for the prevention of home flu), during 36 hours after onset of symptoms in the index case, the incidence of influenza will be significantly lower in family members compared to control group. One of the possible reasons is that the virus shedding often occurs during the first 36 hours so if the preventive interventions start sooner, the probability of home transmission of disease will be lower. Moreover, this study showed that the permanent use of facemask is tolerable and acceptable for both adults and children. In this regard, another study on the effect of non-drug interventions (wearing facemask and hand hygiene) in home environments in Bangkok, Thailand failed to see any effect. Of course, it should be mentioned that index patients who were infected with Influenza (children) slept with their parents without wearing facemask throughout the night, which may block any effect of interventional protection during the day (39). In a random retrospective cluster clinical trial study, Mac-Intyre et al. revealed that less than 50% of participants had the necessary compliance for wearing a facemask and in this group had a significantly lower risk of Influenza-like illness due to infection (25). Results of another study in a social setting such as a student dormitory showed that influenza-like illness was significantly less in the group that used a face-mask, and the group that both used a facemask and maintained hand hygiene compared to the control group. They suggested that adding hand disinfectant does not increase the protective efficacy of wearing a facemask or at least does not increase it significantly (40). Results of these studies show that if index patients and people around them do non-drug interventions such as wearing a facemask and washing their hands in domestic or social settings during the first 36 hours, these can significantly reduce the incidence of respiratory infection in people around them. One of the important religious rituals is Hajj, in which large numbers of people from different countries congregate in a particular region. Thus, it naturally increases the risk of transmitting respiratory viral infections. Results of studies show that use of facemasks by people with the influenza-like illness and those around them (those who were in a tent together) provided more protection against the Influenza-like illness compared to those in the control group, who did not wear protective equipment, and the percentage of infection in each group was 31% vs. 53%, respectively. A significant point in this report was the presence of a positive correlation between duration of facemask use and protection against influenza-like illness, so the incidence of disease in pilgrims who wore facemask more than eight hours a day compared to those who wore a mask for less than eight hours a day was 3% vs 43% (21). Currently, due to the intensity of the COVID-19 pandemic, wearing a facemask is common everywhere, including hospitals and communities (3). In this regard, the results of studies indicate that wearing a facemask is more effective in controlling the spread of infection, especially from asymptomatic carriers. The inward efficacy surpasses outward efficacy and the public's use of facemasks plays a greater role in controlling the source of infection. Of course, wearing a facemask is recommended as a method of infection control and primary prevention for healthy persons (26, 41). Lai et al showed that the use of facemask by HCWs is logical and the use of facemasks, even low-quality cloth masks, by the public should be implemented in the community, immediately. If people can use medical masks, without medical staff running out of PPE reserves, it will be more effective in the prevention of disease transmission. The use of cloth masks by patients or infectious individuals without clinical symptoms prevents infection transmission in the community. Of course, the filtration effects of cloth masks are generally lower than surgical masks. However, if they are well designed (multi-layered cloth masks made of water-resistant fibers with high yarn density and delicate cloth) and used properly (so that the whole face fits in it) they may provide reasonable protection. It has also been shown that these masks can decrease virus exposure, although their ability is much less than medical masks. Therefore, HCWs should not use this type of mask, since the re-sults of studies show that the risk of infection among HCWs who use cloth masks is higher than those who use the medical mask or control group (42). Thus, CDC expressed that at the time of COVID-19 pandemic and due to the limited resources of medical masks, the public could use hand-made cloth masks to optimize facemask stocks. Also, they should be advised to wash their hands daily with hot water and soap, and other appropriate methods. Besides, the public should be educated about their use (27). Therefore, PPE should be selected for special settings and they should be used logically (4). It was thought that N95 respirators have more efficacy in filtering very small particles than surgical masks. However, the results of studies show that in non-infectious health care settings, surgical masks do not have lower protective efficacy than N95 respirators in HCWs (43)(44)(45)(46). However, results of one cluster clinical trial showed that the rate of respiratory infections in HCWs who always use medical mask was double compared to HCWs who always used N95 respirators, and the highest rate of infection was among HCWs who had close contact with patients such as radiologists, followed by nurses. Nevertheless, that study did not have enough power for the results to be generalized, since the rate of observed infection was much lower than expected (24).

Limitations
The limitations of this study included lack of access to fulltext of some studies, lack of data on the effect of facemasks on prevention of each type of respiratory viruses in articles that had studied different viruses, the lack of data on the effect of each type of facemask on reducing the transmission of respiratory viruses and count or percentage of participants who used a facemask. Moreover, some studies conducted on recent viruses (SARS-Cov-2) were not published in English, which is another limitation of the study.

Conclusion
This systematic review showed that using facemasks or respirators aided in preventing the spread of respiratory viruses. The result of the present systematic review showed that using facemasks could prevent the spread of virus. We recommend conducting more studies on the effect of each type of facemask and respirator, individually, and on the prevention of the spread of different viruses. Moreover, we suggest assessing the effect of simultaneous use of masks, duration of using a facemask, and distance between healthy people and the person infected with respiratory viruses.

Acknowledgments
The authors acknowledge Alborz University of Medical Sciences.

Funding and Support
This study did not receive any funding support.

Author contribution
FA and NSH fulfilled an advisory role. ZA carried out the literature survey. NSH edited this manuscript in English. MD commented on the manuscript. All authors passed the criteria for authorship contribution based on recommendations of the International Committee of Medical Journal Editors.

Conflict of interest
The authors state no conflicts of interest.    picornaviruses *These percentages were reported from 37 health care workers who were tested for SARS-CoV-2 and participated in interviews in this study. ** NR: not reported (32) 1.Identification as a randomized trial in the title structured summary of trial design, methods, results, and conclusions (for specific guidance see CONSORT for abstracts) 1 1 1 1 11. If done, who was blinded after assignment to interventions (for example, participants, care providers, those assessing outcomes) and how If relevant, description of the similarity of interventions 0 1 0 0 12. Statistical methods used to compare groups for primary and secondary outcomes Methods for additional analyses, such as subgroup analyses and adjusted analyses 1 1 1 1 13. For each group, the numbers of participants who were randomly assigned, received intended treatment, and were analysed for the primary outcome For each group, losses and exclusions after randomisation, together with reasons